Before diving into speed effects in Adobe Premiere Pro, it’s mission-critical to understand exactly what slow motion is. So let’s back it up: a moving image is a series of still images (frames) played back in a sequence, typically at the frame rate of 24fps or 30fps. You can create slow motion when the shooting frame rate is higher than the playback frame rate (read: greater than 30fps!). Shooting video at 60fps, for example, will yield slow motion playback.
Ideally, you’ll shoot your footage at a high frame rate (and fortunately most cameras will have the option to shoot between 60 and 240fps). To get that really extreme slow motion effect, you’ll need a specialty camera to achieve it.
But what if you’ve already shot your footage at a lower frame rate, you’re working with stock video, or you just need to figure this out in the editing phase? If you’re in any of these situations, this tutorial is for you. Here we’ll look at some tricks to get the best possible manufactured slow motion in Premiere Pro, plus learn how to create speed ramping effects.
Fix it in Post: How Premiere Pro Simulates a High Frame Rate Camera
The problem with artificial slow motion is that in order to bring up that “shooting” frame rate, Adobe Premiere Pro must somehow generate more frames. It can do that by repeating existing frames or analyzing your footage, then automatically generating new frames.
When the software repeats existing frames, the result is a little bit choppy (which has a time and a place, too!). When it generates new frames, imperfections in the interpretation can cause warping and artifacting errors. But no worries — when you understand the tools at your disposal, you can ensure the best results possible.
Speed and Duration
In Adobe Premiere Pro, the Speed/Duration module is the easiest way to create slow motion video. Simply right-click a clip and choose Speed/Duration. To slow down your clip, type a percentage lower than 100%. For example, 50% will play your clip back at half the speed of the original, doubling the duration of the clip.
Alternatively, if you know you want your clip to be a specific duration, type that into the Duration section, and Premiere will adjust the speed accordingly. To adjust speed or duration independently without affecting the other parameter, click the Gang button, so it looks like a broken link.
Speed and Duration adjustments in Adobe Premiere Pro are great for a quick and dirty job: a clip that only needs a slight adjustment, a stylized look, or making something shot slow motion even slower.
How to Use the Rate Stretch Tool
What if you need your clip to fit an exact space in your edit? The Rate Stretch tool allows you to click and drag a clip to an exact duration, and Premiere will adjust the speed to fit the duration. To use the Rate Stretch Tool, just select it, and click and drag either end of your clip to the desired length. Premiere Pro will update the speed of the clip.
Create a Speed Ramp With Time Remapping
Speed ramping is the process of progressively changing the speed of a clip over time. Here’s an example using this clip of a dancer:
Before getting started, click and drag to increase the height of the video track you’ll be working with, so you can see what you’re doing in the next steps. Right-click the clip, and select Show Clip Keyframes > Time Remapping > Speed.
A horizontal band appears that controls the speed of the clip. Dragging the band up and down will adjust the speed (and in turn, the duration) of the entire clip.
To create a progressive speed change you’ll need to add keyframes. For an effect where the speed ramps up or down to highlight a motion and then resumes normal speed, you’ll need to create two keyframes, essentially separating the clip into three sections. Command + Click (Mac) or Control + Click (PC) the band to create keyframes. Click and drag that middle section up for fast motion, down for slow motion.
At this point, the speed change is abrupt. To smooth the ramp, click and drag your keyframe to split it. Use the Bezier handles to smooth the effect further. Play around with the ramp until you’re happy with the look.
The Optical Flow feature can help smooth your slow motion effect to make it look more like you shot at a higher frame rate.
When enabled, Premiere Pro will use existing frames to intelligently generate new frames to go in between your existing ones. The result is smooth rather than choppy motion.
Let’s look at an example of slow motion created using the Speed/Duration module with the default Time Interpolation (Frame Sampling):
When using Frame Sampling, Premiere Pro duplicates existing frames to create the slow motion effect. The result works, but it’s a bit choppy. Compare with this example, using Optical Flow. You can really see the difference at the beginning of the clip when the dancer goes up on pointe.
To enable Optical Flow when using the Speed/Duration controls, change the Time Interpolation to Optical Flow. After making this change, you’ll have to render the footage before playing it back. Choose Sequence > Render In to Out.
Using Optical Flow to smooth a speed ramp is just a little bit different. Right-click and choose Time Interpolation > Optical Flow. Render.
But Optical Flow isn’t perfect—because Premiere Pro is generating entirely new frames, some issues like warping and artifacting can occur. For best results, shoot against a simple, static background. The more detail and movement Premiere has to interpret; the more likely something will be off.
Level Up With Plugins
If you frequently work with slow motion and high frame rate cameras, it could be worth it to invest in software designed specifically for the task. For precise retiming, you can try a plugin like Twixtor that will essentially do the same thing as Optical Flow but at a higher level. Starting at $330, however, it’s an investment and one that still won’t replace a high frame rate camera. If you only work with slow motion on occasion, you’ll be just fine adjusting in Premiere Pro.
In short, if you’re trying to be the next Slow Mo Guys, you’re going to need to invest in a fancy camera. If you need to retime a clip to fit an edit, emphasize an action in your YouTube Video, or create a little drama, Premiere Pro alone or in tandem with some 60fps footage will do you just fine.
There’s a lot you can do with speed ramping and slow motion in Adobe Premiere Pro – so have fun experimenting with these different slow motion effects!